Lathe Rear Tool Post For Parting Off

Why should parting off from the rear and running the lathe in reverse be any better ?

Probably because there is less wear on the rear side of the ways? They are not advocating running the lathe backwards in this thread (a 'must not do' if the spindle is threaded for chuck attachment, as stated above)?

While facing from the centre, the cutter will be using a different part of the cutting edge, so perhaps that is the reason?

Thread is now a bit muddled, perhaps, as it started with an inverted parting tool with the lathe direction reversed and changed to an inverted tool, at the back, with the lathe running in the normal direction.

Certainly it may be simply the question of an inverted cutter not loading up with swarf/chips and either riding on the already cut metal (or the typical galling while cutting aluminium when hot metal sticks to the cutter tip).

I've not tried using an inverted cutter from the back, but parting off was never an easy task until I changed to my 'old iron' lathe. So now there is very little incentive to change as parting is so much easier and predictable.

Possibly there is something to do with rigidity on small lathes, but in that case why not do all turning from the back with the lathe running forwards? There may be more questions than answers on this one! But if it works for you, then so be it - parting is not a large percentage of lathe work, after all.

Just to avoid ambiguity. In my video the lathe is not running in reverse. There are three things that I can think of that are different from parting off from the front with respect to what I have shown in the video.

Gravity is in the other direction w.r.t. to blade orientation.
The lead screw is in tension rather than compression when the tool moves towards the work.
The tool post is just one lump of steel, with less bits and components.

David

I have been watching this thread with interest. My lathe cross slide was well worn along with the feed screw and nut. Earlier this year I made a new beefed up cross slide and bought a length of trapezoidal threaded bar and a nut. With all this fitted and minimal backlash parting from front toolpost mounted holder (HSS Blade) was better but still scary at times. I have just bought from Arc Eurotrade a 2mm tipped parting blade and made a rear mounted toolpost. First thing I tried was 1" aluminium at 1100 RPM, the cutter flew through so next up 1" EN1A at 780 RPM with the same good result. I followed this by parting off 20 washers from 16mm 316 stainless at 780 RPM. I am more than pleased with the result and when the spare tips arrive will try parting with the powered feed.

With power fee you will probably be able to up eh RPM. The problem I found was being able to hand feed fast enough to keep up at higher rpm.

You can turn from the rear. Just add another toolpost and invert the tool. It's usually reserved for parting off even on lathes that don't have any problems doing it. Many things that are turned up need parting off so it saves fitting the tool.

John

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I made myself a Four Way Rear Tool Post for my lathe (An ETR BL12/24 - a Warco BH600 or Chester Caftsman lookalike).

The parting tool is mounted inverted, in a resilient holder, and with the lathe run, fairly slowly, in Forward, as normal.

In nearly a dozen years of use, there have been very few jams, and the 3/32" blade has never broken. To make matters worse, it is ground at an angle to produce no "pip" on the back of the workpiece, which should invite a jam up because the swarf is wider than the groove!.

I have even, on occasions, used a power feed of 0.0022"/rev without problems.

A steady drip feed of soluble oil, from a bottle placed above the lathe, does help

In contrast, a 1/16" blade, mounted solidly, in the Front Tool Post broke several times, so much so that I cannot recall when it was last used.

The other spaces carry toolbits to produce for Front and Back chamfers.

The Back Tool Post very rarely comes off the Cross Slide, usually to take it to exhibit at a show.

Definitely the way to go!

Howard